Global imports of Iranian crude in April averaged 1.11 million barrels per day (bpd), the Paris-based IEA said in its monthly Oil Market Report released on Thursday, down 180,000 bpd from March.

"Imports of Iranian crude reached a 20-month high of 1.58 million barrels per day in February but have since edged lower," the IEA, adviser to 29 industrialized countries, said in the report.

Under an interim deal signed in November between Iran and six world powers that came into effect on Jan. 20, known as the Joint Plan of Action (JPOA), Iran's exports are supposed to be held to an average 1 million bpd through July 20.

Signs of higher Iranian sales in late 2013 and early 2014 have led to concerns in Washington that a softening of sanctions has given Tehran's economy a boost.

But officials in the Obama administration have said they expect Iran's oil sales to fall in coming months and average 1 million bpd over the entire six-month period.

In April, China, South Korea, Turkey and Syria increased imports of Iranian oil, although this was more than offset by reduced volumes to India and Japan, the IEA said, citing preliminary data.

The biggest increases were by China, which boosted imports by 60,000 bpd to 615,000 bpd, and South Korea, which imported 130,000 bpd, up 70,000 bpd, the IEA said.

India cut imports by 185,000 bpd to 200,000 bpd and Japan by 105,000 bpd to 35,000 bpd, it said.